


Impulse

by kittyhittyrh



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap (Undertale), Anal Sex, Blue/Dream Child, Daddy Kink, Don't do it without lube, Dream Sans Child, Dusttale Sans (Undertale), Dusttale Sans/Underswap Sans (Undertale), First Time, Fluff and Smut, Human, Light Bondage, M/M, Magic, Mentioned Underswap Napstablook, Multi, No Lube, Numbtale Sans, Other, Protective Mama Blue, Salty Blueberry, Shine (Undertale), Shyness, Two Shot, Underswap Mettaton (Undertale), Underswap Papyrus (Undertale), Underswap Sans (Undertale), Underswap Sans Child, Yandere
Language: English
Status: Completed
Published: 2020-06-26
Updated: 2020-06-25
Packaged: 2021-03-04 06:55:30
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 2
Words: 3,583
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24919429
Author URL: https://archiveofourown.org/users/kittyhittyrh/pseuds/kittyhittyrh
Summary: Shine will do anything for Eclipse, without a second thought.
Relationships: Mettaton/Papyrus (Undertale), Papyrus & Sans (Undertale), Sans (Undertale) & Original Male Character(s), Sans (Undertale)/Original Male Character(s), Sans/Sans (Undertale)
Kudos: 3
Collections: Incantale, Shine and Eclipse





	1. Chapter 1

All this started because most of the kids were out with the exception of Shine. Bluescreen, Pastel and Blueprint were visiting with Ink and Error, Ink had also agreed on taking Sprinkles for a bit. Calibri was spending the night with Napstabot. Shine was given the option about going with Dream or Ink, he was adamant about staying with Eclipse. Paps used this as an opportunity to ask Blue if he and Dust would go on a double date with him and Happsta. Blue was reluctant at first because he didn’t want to leave Shine and Eclipse alone. He still was salty over the whole incident and what made it worse was that since Eclipse didn’t want to go back to his universe (which was justified) that he was staying with them because Shine wanted him there. It made Blue uncomfortable that no one else seemed to be concerned over it. Paps would tease him for it, saying he sounded like him while Dust would listen but not offer anything. Happsta tried her best to not be involved. He tried talking to Dream about it too. Dream was just happy that Shine was experiencing emotions and told him to let it go. Neither the less, Paps somehow managed to convince Blue who talked to Dust and he agreed.  
When they left Blue had all but threatened that Shine better be the way in the same shape he was and in his own room when they got back, much to Paps’ amusement and even a bit of Dust’s as well. Eclipse seemed to brush him off while Shine was embarrassed and confused but mostly confused. He and Eclipse had never kissed let alone done anything like that… Shine had managed to get Eclipse to cuddle with him a few times though after sneaking into the guest room and maybe watching him sleep until Eclipse was awoken by a nightmare. So Shine really wasn’t sure what his mother was thinking.  
~  
An hour or so later Shine had fallen asleep against Eclipse, who had an arm around him, on the couch. They had been watching whatever was on TV. During the time while Shine was asleep he had been snuggling against Eclipse so much that the other figured it would be best to just pull him onto his lap. The closeness was still pretty new to Eclipse, but he didn’t exactly mind. He held Shine close and subconsciously began playing with Shine’s hair, barely watching whatever was on TV.  
Shine woke up about a half an hour later, he looked around groggily, before realizing where he was, his face turning red. Eclipse petted his head, a bit, “Sleep well, Sunshine?...”  
Shine nodded slightly, his face red, he hid his face into Eclipse’s shoulder. Eclipse petted his head again, Shine took a deep breath. Getting comfortable against him, Shine nuzzled his shoulder. Eclipse’s hand slipped down and lightly rubbed his back, making the younger suddenly giggle.  
Eclipse showed a slight smirk, continuing, “Ticklish?”  
Shine giggled more, “I-I guess… Heehee…”  
Eclipse’s fingers lightly tapped at Shine’s back making him giggle more. With each giggle Eclipse’s fingers moved up or down and a little faster. This continued until Shine was curled up in a ball against Eclipse, laughing so hard he could barely breathe, “St-stop haha! Cl-Clippy, please! Hahaha!”  
The small smirk was still on his face, Eclipse stopped tickling Shine. Shine breathed a little heavily, catching his breath.  
“Are you okay?...”  
Shine nodded, uncurling and relaxing against him, “M-mhmm.”  
They were silent for a little while.  
“U-uhm, E-eclipse,” Shine broke the silence.  
“Hm?”  
“...W-we’ve never kissed…” Shine said, his face flushing.  
Eclipse blinked, “No, we haven’t… Do you… want to?”  
Shine kissed his cheek, still blushing. Eclipse blinked, “Kid, that's not wh-”  
Shine actually kissed him this time. Eclipse froze while Shine continued to kiss him, pressing close against him. Eclipse was still frozen, Shine pulled back, he blinked, disappointed, “Y-you didn’t kiss back… d-did I do something wrong?”  
Eclipse slowly shook his head, he was quiet… there was a barely noticeable blush on his face.  
“E-Eclipse? S-say something… I-I’m sorry! Pl-Please don’t be m-mad at me… I-I won’t do it a-again…” Shine whimpered, sitting back.  
“W...ait,” Eclipse spoke a little too late and Shine sat back, he froze… he felt something poking him. His eyes widened and his face flushed completely when he realized what was going on.  
“...O-oh my… I-I’m so-”  
“...S-stop apologizing… J-just don’t move…” Eclipse said.  
Shine bit his lower lip, he sat as still as possible, they were quiet. Eclipse let out a shaky breath.  
Shine suddenly spoke, “D-do you want me… to h-help?”  
“K-kid… the only way to ‘help’ is for us to have sex… your mom and uncle would try to kill me… and I do-” he let out a small moan as Shine shifted, leaning forward and kissing him.  
Shine pulled back slightly, smiling slightly, “Clippy… I want to help you. It’s okay… and they don’t have to know… Besides… knowing Uncle Paps and Aunt Happsta… they’ll all be out for a few more hours and they’ll all be having too much of their own fun to worry about what we’re doing…” he kissed Eclipse again.  
Eclipse pushed him back a bit, “Are you sure, Kid?... If we do this… I won’t stop unless I hurt you…”  
Shine blinked, he spoke without thinking at all, “You won’t hurt me. Please let me help you.”  
Eclipse sighed, before pulling him into a quick kiss, then he picked him up and carried him upstairs to the guest room, which was basically his room now.


	2. Chapter 2

Eclipse used his magic to open the door to his room, carrying Shine inside before closing and locking it behind them. His face still lacked positive emotion, but Shine could tell that there was a whole mess of feelings within him, both positive and negative.  
Shine was nervous, the emotions he was receiving from Eclipse were and weren't helping. He bit his lower lip. It was weird though. He wasn't nervous about what was going to happen, he was nervous that he wouldn't be able to please Eclipse... Okay so it wasn't that weird.  
Eclipse placed Shine on his bed, which was actually pretty soft. Shine stared up at him, unsure of what he should be doing... He kind of wished he had finished that conversation with Napstabot when he was younger right about now.  
Eclipse was staring at Shine, his violet eyes full of lust. He started off slow, gently touching Shine's cheek before kissing him. Shine blushed and kissed back.  
Eclipse slipped his tongue into Shine's mouth, slowly pinning him down. Shine let out a surprised noise, blinking a couple times, he decided to try pushing his tongue against Eclipse's.  
Eclipse let out a small moan, allowing their tongues to wrestle together. His hand slowly traveled up Shine's shirt, lifting it slightly as it moved. Shine tried not to giggle at the tickling feeling of Eclipse's fingers and the edge of the shirt, instead he squirmed a bit, and deepened the kiss.  
Eclipse let out another moan as his hand wandered around Shine's stomach and chest. Once Shine started to get used to the feeling he wrapped his arms around Eclipse's neck, but not before pulling his long blonde and black hair from it’s ponytail. Eclipse’s hair splayed down his back as they continued to kiss.  
Eclipse pulled away for a moment to slip Shine's shirt off of him. He stared down at him, blushing, "Fucking hell, you're so cute..."  
Shine blushed, unsure what to say, he tried to cover his chest, he was pretty sure he was feeling a bit insecure.  
"There's no need to hide from me, Shiny..." Eclipse said, his voice a little bit… deeper than normal.  
Shine gulped a bit, looking up at him innocently. Eclipse was staring down at him, then took off his scarf and shirt to try and make Shine feel a little bit more comfortable.  
Shine blushed and shyly reached out to touch Eclipse's chest. Eclipse blushed a little bit.  
"S-so um... It's probably pr-pretty obvious... B-but I have no clue what I'm d-doing... You're go-going to have to walk me through this..." Shine spoke, looking away a bit.  
"Yeah, I know. Just leave everything to me," Eclipse said, giving Shine a small kiss on the lips before going down and kissing his neck.  
Shine shivered, letting out a squeak. Eclipse chuckled a little bit and gave Shine's neck a small bite. Shine let out a small gasp. He began randomly biting and kissing around Shine's neck.  
Shine squirmed a bit, letting out a soft moan. He started sucking on a spot on Shine's collar bone. Shine whimpered, it wasn't a painful one though... It was more uncertain than anything. Which made sense because of how new this all was to him.  
Eclipse left a few more marks on Shine's neck before lifting his head up, then going to get something from his drawer. Shine blinked and sat up to watch him, curious.  
"I want to ask you something, Shiny. Do you know what kinks are?" Eclipse asked.  
Shine blinked and nodded, that had been a part of what Napstabot had told him, "Y-yes."  
"Alright… another question. Would you be okay if I tied your hands together?..."  
Shine froze a moment, then shook his head, "I d-don't mind..." he bit his lower lip, slightly, "I-I mean at least you're asking this time... Aheh..."  
Eclipse blushed a little, "Because this time I’m doing it out of love instead of just forced company.”  
Shine blushed, Eclipse took a bit of rope out from the drawer. Shine bit his lower lip, fully this time. Eclipse walked over to Shine, "Are you sure you're comfortable with this?"  
Shine nodded, seeming a bit sheepish, "O-of course."  
Eclipse took a deep breath and nodded before starting to tie Shine's hands to the head of the bed. Shine let him, gulping a bit. Eclipse looked down at him once he was done, blushing, "Damn..."  
Shine squirmed a little, starting to feel insecure again.  
"Shine? Are you alright?..."  
Shine nodded, shaking a bit, "I uhm... I'm just feeling insecure... I-I don't know why..."  
"Alright… just take it easy..." Eclipse said, his hands went down to Shine's pants.  
Shine blushed deeply, his hands clenching and unclenching a bit. Eclipse slowly started pulling them down. Shine watched, unsure if he should try to help, but he really wasn't how he could help with no use of his hands. Eclipse got Shine's pants off, along with his boxers. Shine shivered a bit, he was a bit cold and became nervous again.  
Eclipse blushed deeply before his hand gently grabbed Shine's dick. Shine gasped, biting his lower lip, "Mmm~"  
"Like that~?”  
Shine nodded, letting out a shaky breath. Eclipse smirked, starting to move his hand. Shine let out a soft moan. Eclipse kissed him again as he continued to jerk Shine off. He was holding himself back, not wanting to hurt Shine at all.   
Shine kissed back, straining the ropes a bit, he wanted to hold Eclipse and to touch him too... He didn't like all the attention, “Clippy, I want to touch you... I-I don't want to be tied up an-anymore." His voice was straining a bit.  
"Hnn… fine," Eclipse said, untying Shine. While he loved seeing Shine being tied up and at his mercy, he didn't want to scare Shine or make him uncomfortable. He cared too much about him to do that.  
Shine smiled and wrapped his arms around Eclipse, kissing him.  
Eclipse kissed him back, his hand never stopping as his other one rubs Shine's back. Shine moaned into the kiss, his one hand moving down to pull at Eclipse's pants.  
Eclipse moved his hips slightly to help Shine get his pants off. Shine pushed them down as far as he could, his hand faltering a bit when he went for Eclipse's boxers as he suddenly gave a small buck into Eclipse's hand, letting out another moan. Eclipse let out another chuckle, moving his hand a little bit faster.  
Shine broke the kiss, "Ah... E-Eclipse~" He buried his face against his shoulder; his hand that was supposed to be trying to take off Eclipse's boxers instead went to the bed and he gripped the blankets tightly.  
"Does it feel good, Kiddo~?" Eclipse asked.  
Shine nodded, frantically, "Y-yes-s.." He bucked into his hand again.  
Eclipse smirked a small bit before stopping his hand. Shine let out a whimper, "Wh-why did you st-stop?"  
Eclipse moved down and took Shine's dick into his mouth. Shine froze up and gasped. Eclipse started sucking it. Shine bit his lip, trying to hold back a moan. Eclipse was already deepthroating him, as if he had done this before. Shine whimpered, his eyes closing, he let out a moan. His mind has pretty much been screaming at him that he didn't know this was a thing, especially a really good feeling thing, "E-eclipse~"  
Eclipse let out a slight moan as he continued to suck. He was pretty amused with himself, knowing he's seen Shine express more emotion than his parents ever did. Shine arched his back a bit, letting out another moan, he bucked his hips slightly. Eclipse used his tongue to tease Shine a little bit.  
"Ah~ Eclipse!"   
Eclipse pulled his mouth away, making Shine whimper at the loss.  
"I think it's about time for you to do the same."  
Shine gulped, "Th-the same?"   
Eclipse nodded, "Yes."  
Shine bit his lower lip and nodded, "O-okay..."  
Eclipse slipped his boxers off. Shine blushed, looking away a bit.  
"Are you alright, Shiny?" Eclipse asked.  
"I-I'm supposed to look, h-huh?" his face was completely flushed.  
"Yes..."  
Shine looked, he bit his lip, face somehow blushing more.   
"You don't have to if you don't want… I don't want to force you into anything," Eclipse said, petting his head a little.  
Shine blinked, "I-I'll do it.. I want to m-make you happy."  
"Kid… my happiness isn't that important to me." Eclipse said.  
"But it is to me! You make me so happy just to be next to you! I want you to feel the same!" Shine responded, tearing up a bit, "I... I love you and I want you to be happy!"  
"Kid..."  
Shine hugged him, seeming at that moment to forget that they both were naked. Eclipse looked down at him before hugging him back. Shine whimpered a bit into Eclipse's shoulder.  
Eclipse held him closer, "I… I love you too, Shiny..."  
Shine blinked, pulling back a bit. He smiled as his eyes were shining a bit and he actually seemed to fit his name for once. He leaned in and kissed him. Eclipse kissed him back, running a hand in his hair.  
Shine shivered a bit and continued to kiss him. After a little while, he decided to try something unexpected, he tried to add his tongue into the kiss.  
Eclipse blushed a little bit before doing the same, letting their tongues wrestle slightly. Shine blushed, he let out a small contempt breathe through his nose, pressing close against Eclipse, he froze slightly remembering their lack of clothes finally.  
Eclipse blushed a little bit, pulling away, "Heh… w-we're still naked..."  
Shine nodded, "Y-yeah we are... I-I don't mind though.... th-that is if you don't..."  
"Of course I don't… but… shall we move on with… what we were planning?"  
Shine bit his lower lip and nodded, "M-mhm..."  
Eclipse laid Shine down again and got on top of him.  
"W-wait... I was s-supposed to do the same for you, right? I was su-supposed to suck-" he stopped speaking honestly unsure if he could finish the statement.  
"We can skip that. I want to get on with this..."  
"N-next time?" Shine asked.  
"Next time."  
Shine nodded and smiled, "O-okay."  
Eclipse nodded and positioned himself, "This may hurt a little bit at first..."  
Shine bit his lower lip and nodded. Eclipse took a deep breath before slowly pushing into him, groaning. Shine squeezed his eyes shut, letting out a pained noise. Eclipse stopped to let Shine adjust to him. He was only about halfway in, "F-fuck...."  
Letting out a shaky breath, Shine clung to him, "Y-you said it would h-hurt a little..." He whimpered.  
"I-I'm sorry… b-but I promise it will get better."  
Shine nodded, slightly, "A-alright..." he lets out another whimper.  
"J-Just tell me when I can push in more..."  
"G-go on... I-I'll be okay..." Shine was shaking a bit.  
Eclipse took a deep breath before pushing in more.  
Shine let out a yelp, he bit his lower lip, hard... it started to bleed a bit.  
Eclipse panted a bit, "Th-there, I'm all in..."  
Shine's nails were digging into Eclipse's back and hair, his teeth still in his lip. Eclipse holds him, trying his best to not move and hurt him more. Shine took a deep breath, removing his teeth from his lip. He could taste the blood, he was quiet though, shaking from both the pain of the penetration and the pain now in his lip. Eclipse was petting his head, trying to soothe him as best he could.  
"I-I'm fine... I-I just wasn't ex-expecting it to hurt that m-much..." Shine said, trying to even his breathing.  
Eclipse kissed his forehead, "It'll be okay… I won't move until the pain starts going away… I don't want to do anything bad to you..."  
"N-no, I-I'm okay... Y-you can move," He gave a shaky smile.  
"A-are you sure?"  
Shine thought a moment before giving Eclipse's shoulder a small kiss and he nodded, "Y-yeah... I tr-trust you won't h-hurt me... Or at-at least on purp-pose..."  
Eclipse blushed, "O-Okay..." He started to slowly move.  
Shine tried not to bite his lip again, it didn't exactly hurt now; it just felt really uncomfortable. Eclipse was keeping a slow pace, not wanting to hurt Shine.  
Shine let out a shaky breath, "C-can you go a-a little faster?..."  
Eclipse nodded a little bit, going a little bit faster. Shine let out another shaky breath, it was feeling less uncomfortable now, but not exactly pleasurable either, there was something missing.  
Eclipse let out a small moan. Shine was so tight and it felt really good to him.  
Shine blushed, "A-a little more please..."  
Eclipse nodded, going a bit faster. He was glad that Shine was starting to feel better.  
"M-mmm~" Shine was starting to feel a small bit of pleasure but there was still something missing, he decided to try pushing back.  
Eclipse looked at Shine, his face flushed brightly with his own blush.Shine gave a shaky smile, before suddenly letting out a gasp of pure pleasure; his spot had been hit.  
Eclipse smiled a little, "I'm guessing it's right there~?"  
Shine nodded, something clicking in his head at that moment, "Y-yes... D-Daddy~"  
Eclipse's eyes widened a bit, his blush getting darker. Shine let out another moan, arching his back a bit. Eclipse moaned and started going faster and harder, making sure to try and hit that spot over and over.  
"O-oh, D-Daddy~!" Shine moaned, his nails digging into Eclipse's back slightly.  
Eclipse let out another loud moan, going even harder, "F-Fuck, Shine~!"  
"A-ah! D-Daddy, more please~!" Shine tried to match his pace.  
Eclipse started biting at Shine's neck as he went even faster and harder, the bed creaking from their moments.  
Shine gasped, "O-oh my god! H-hah!" He moaned, "G-god yes! D-Daddy~! Ah!" He tilted his head back to try to expose more of his neck.  
Eclipse groaned in pleasure as he kept biting around Shine's neck, leaving marks everywhere. Shine shivered, his eyes closing, his movements picking up as he tried to get more pleasure, "D-Daddy, -ah- please d-don't stop~! It's so goo- ah!- good!"  
Eclipse groaned, “I-I don't plan on stoppin', Shiny~"  
Shine moaned, loudly, "This feels so g-good, D-daddy~! Ah~!"  
"Fuck yeah it does~" Eclipse groaned before kissing Shine, slipping his tongue in immediately.  
They both moaned into the kiss, Shine pushed his tongue against Eclipse's. Shine arched his back, suddenly biting Eclipse's lower lip. Eclipse groaned a little bit. Shine licked the bite mark. Eclipse moaned a little bit, smiling a bit at Shine. Shine blushed, letting out another moan. Eclipse moaned too, starting to feel close.  
"D-daddy~ I think... I-I think I'm reaching my l-limit," Shine whimpered, letting out another moan.  
"I-I am too, Kiddo~" Eclipse moaned.  
Shine kissed him again, nails digging into his back, hard. He broke the kiss quickly to let out one last loud moan and he came. Eclipse gasped and moaned as he felt Shine tighten around him suddenly. He quickly pulled out and came as well.  
Shine panted, laying back on the bed. Eclipse panted a bit, laying down next to Shine, “Holy… shit..."  
Shine let out a breathless giggle.  
"That was amazing..." Eclipse said  
Shine smiled, curling up against him, "M-mhmm."  
Eclipse put an arm around him. Shine sighed happily, running a hand over Eclipse's chest, he giggled suddenly.  
"Hm?"  
Shine kissed the bottom of his jaw, "So you like to be called, ‘Daddy’ huh?" he gave a... mischievous?... smile.  
Eclipse blushed, "U-uh, yeah?"  
Shine giggled, nuzzling him, "Good to know~"  
"I have a feeling you're going to exploit it, aren't you?"  
"Just when we're alone~ I promise," Shine grinned.  
"Good."  
Shine gave him a soft kiss before snuggling against him.  
"Let's get some rest now, okay, Kiddo?"  
Shine nodded. Eclipse smiled and held Shine close before falling asleep. Shine let out a content sigh before drifting into sleep also.


End file.
